Re: Monograph on Olive Leaf Focuses on Pharmacological Studies
Monograph. Olive leaf. Altern Med Rev. 2009;14(1): 62-66.
Olive (Olea europaea) leaf, the first botanical
medicine mentioned in the Judeo-ChristianBible,
was used by the ancient Greeks for fevers. In 1843, it was reported that a
bitter substance in olive leaf tea was effective against malarial fever. Since
the early 1900s, olive leaf extracts (OLEs) have been found to be
antimicrobial, antioxidant, and hypoglycemic, and to have cardiovascular
benefits in animals and humans. Primary constituents are secoiridoids
(oleuropein and its derivatives), hydroxytyrosol, and various polyphenols,
triterpenes, and flavonoids. Oleuropein is responsible for many of olive leaf's
effects. Also found in olive fruits and oil, it is more concentrated in the leaves.
Olive leaf components in vitro inhibit many viruses, e.g.
pseudorabies, some forms of polio, cold and influenza viruses, and human
immunodeficiency virus (HIV). One constituent, calcium elenolate, inhibited
nearly every virus studied, including coxsackie, encephalitis, and two strains
of leukemia. Olive leaf inhibits
assembly of the cell membrane and stops viral shedding. Anecdotal reports
suggest that gargling with olive leaf tea may relieve sore throat, and taking
OLE at the first sign of colds or flu may shorten symptom duration. Calcium
elenolate given to hamsters with influenza cured infection. Anecdotal reports
of benefits to HIV-positive individuals date to 1996. OLE is widely used in
this population to strengthen the immune system, reduce viral load, relieve
chronic fatigue, treat Kaposi's sarcoma and Herpes
simplex, and reduce adverse side effects of antiretrovirals. Some patients
have reported reversal of HIV status. Treating HIV-1-infected cells with OLE
upregulated apoptosis inhibitor proteins, calcium and protein kinase C pathway
signaling HIV-1 infected cells treated with OLE ornithine suppressed
cell-to-cell HIV transmission. No clinical trials have been conducted on OLE as
a viral treatment.
OLE inhibits many gram-negative and gram-positive bacteria,
yeasts, and parasites, including malaria-causing Plasmodium falciparum. It may inactivate cellular enzymes needed for
replication, or directly attack bacterial cell walls. Clinical trials have not
evaluated olive leaf against bacterial pathogens. It inhibits food-borne Bacillus cereus in vitro and in humans, altering
germinating spores to delay growth. In vivo, in multi-drug resistant Pseudomonas aeruginosa, oleuropein reduced
oxidative stress and prolonged survival.
OLE was reported to be hypotensive in 1951. It suppresses
the L-type calcium channel directly and indirectly, causing vasodilation and
reducing blood pressure. Oleuropein individually is also a vasodilator. OLE is
antioxidant and anti-inflammatory. It had the highest radical-scavenging
ability of 55 medicinal herbs in one study, more than twice that of green tea (Camellia sinensis) or milk thistle (Silybum marianum). Oleuropein reduces
oxidation of low-density lipoprotein (LDL) in vitro and in vivo. OLE inhibits
platelet aggregation and thromboxane A2 production. All of these
effects contribute to olive leaf's cardiovascular benefits, as do its
hypoglycemic effects. Given to rats with induced diabetes, it reduced blood
glucose levels significantly, raised insulin levels, and increased peripheral
glucose uptake dose-dependently. OLE components luteolin and oleanolic acid
inhibited postprandial glucose increase in vivo. OLE given to hypertensive rats
at 100-1000 mg/kg for 2-6 weeks significantly lowered mean arterial pressure
and heart rate. Given to salt-sensitive, genetically hypertensive rats at 60
mg/kg, it prevented severe hypertension and atherosclerosis (most likely by
suppressing inflammation) and improved insulin resistance.
A human clinical trial studied OLE's effects on blood
pressure in 40 borderline hypertensive pairs of identical twins. Twins from
each pair were assigned to control or to one of two groups receiving 500 or
1000 mg/d OLE for six weeks. Mean blood pressure was unchanged for control and
500 mg groups, but the 1000 mg group had a significant decrease in mean
systolic blood pressure (from 137 +/- 10 to 126 +/- 6; P<0.01). Another
clinical trial (n=30) reported significant decreases in blood pressure in
hypertensive patients given 400 mg aqueous OLE four times/d for three months.
In vitro, olive leaf polyphenols significantly suppressed platelet-ATP release
and platelet aggregation in a dose-dependent manner.
In vivo, OLE in doses of 100, 250, and 500 mcg/d increased
T3 levels dose-dependently and significantly reduced circulating thyroid
stimulating hormone after 14 days, suggesting a possible use in hypothyroidism.
Due to OLE's hypotensive and antiplatelet aggregation
effects, caution should be used if also using blood pressure lowering or blood
thinning medicines. In vivo studies report no toxicity even at high doses;
studies in human cell lines likewise have found no toxicity. No studies have
been undertaken in pregnancy or lactation. OLE is best taken with food to avoid
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